Radioactive iodine is used for the diagnosis of distant and local metastases of thyroid cancer and therapy of thyrotoxicosis and thyroid cancer. Because of the high iodine content of the American diet, the efficacy of radioiodine is diminished unless that patient is placed on a strict low iodine diet. This diet which consists of freshly prepared meals and homemade breads and pastas is nearly impossible to follow with the American dietary habits of eating in restaurants and using convenience foods. After review of the iodine content of currently available foods, the objective of this study is to develop and test a convenient and palatable out-patient diet to decrease iodine intake and excretion to less than 50mcg/24hrs in normal volunteers and patients undergoing routine radioactive iodine diagnostic scanning or therapy for thyrotoxicosis and thyroid cancer.